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Open Roads Forum  >  Tech Issues

 > Pulling more than 50 amps ?

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Gdetrailer

PA

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Posted: 08/02/20 11:17am Link  |  Quote  |  Print  |  Notify Moderator

wa8yxm wrote:

Gdetrailer wrote:


You however cannot "combine or connect" L1 and L2 together because they are out of phase (one positive and one negative going). Adding two voltages out of phase CANCELS the voltage and in this case creates a huge short and the result would be zero volts.


Though you are correct. 100% and that was a good post I will comment on this paragrapy.
Wrong point of view
When we talk about "Combining" we mean one leg is fed to the OUTLET so there is L-1 and L-1 not L-1 and L-2
You were looking at it from the other side. You are correct that if you try to hook L-1 to L-2 smoke fire and sparks (or tripped breakers) will ensue.

But some "Cheater Parks" only run one leg to the box or so I'm told.


The key is "so you been told"..

There is no way ANY park which has a 50A 120/240 socket could have connected only ONE hot to both L1 and L2 terminals in the box and have been "legal". That would have had to be an pirate connection, I think you have been told a few "tall tales" from folks who don't understand how the mysteries of electric work.

Why?

Simple, using only one of the split phases can easily overload the NEUTRAL wire on your shore cord and even the campgrounds own Neutral.

That would never have passed the POCOs inspector and the POCO REQUIRES ALL connections to the grid to be INSPECTED before any power is applied.

The split phase setup allows one to use the same size neutral wire as the hot phase (L1 and L2). This is because the voltage and current on the L1 and L2 are 180 degrees. The same thing as the voltage, the current on L1 goes up when the current on L2 goes negative. That has the effect of canceling out the current seen on the neutral.

To visualize this you would have to imaging having only a purely restive load like say two 120V 100W incadescent bulbs wired in series. The voltage and current are evenly divided and flowing only on L1 and L2 and zero current would be flowing on the neutral (balanced circuit).

Now, if one of the 100W bulbs were to be replaced with a 50W bulb, you would have an unbalanced circuit and because you have the neutral the 100W bulb still pulls 100W and the 50W bulb pulls 50W and the neutral will have 50W on it..

In your example, using only one of the Split phases two 100W bulbs are in parallel and the neutral carries full 200W. Very easy to overload the neutral.

Combining L1 and L2 on the shore power socket would mean the Neutral would now see a potential of a 100A worth of current (basically paralleling the TWO 50A breakers) , that is going to cause fires. Campground would end up being liable and on the hook for burning down someones RV..

Now, if you are talking those portable "cheater boxes" where you use a 30A 120V and 20A 120V plug in to the shore power, 30A and 20A add up to 50A and will not overload the neutral.. Those CAN use the SAME phase or L1 and L2 but in most more modern parks you WILL run into issues with the 20A plug in having a GFCI which will most likely not like that setup and be a tripping issue.

hypoxia

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Posted: 08/02/20 12:25pm Link  |  Quote  |  Print  |  Notify Moderator

valhalla360 wrote:

I've yet to come across one of these rigs that have 240v appliances. I'm sure they exist but kind of like hen's teeth

Mine has a 240 VAC Dryer but no hens teeth. The AquaHot uses both sides with two 2000 watt elements but they are 120 VAC elements so I guess that doesn't count.


Jim

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valhalla360

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Posted: 08/02/20 03:19pm Link  |  Quote  |  Print  |  Notify Moderator

BB_TX wrote:


From the OP:

Our park electrician says that some of the big rigs with 3 ACs and electric everything can sometimes draw more than 50A from a 50A pedestal.

A very simple statement regardless of the intent behind it. And that simple statement is absolutely true, at least until either the park 50 amp breaker trips, or the RV 50 amp breaker trips. And the voltage being used is entirely irrelevant. Doesn't matter whether the RV has any 240 vac appliances or if they are all 120 vac.

Boggles my mind that this has turned into a 9 page (an counting) debate about an "idiot electrician" making a very simple and very true statement and everyone turning that into their own personal interpretation as if they know more about what he was referring to than the electrician himself.


Nothing in your quote states they were referring to 240v operations. Even for big rigs, 240v appliances are very rare.


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wa8yxm

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Posted: 08/02/20 03:27pm Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:

Y park which has a 50A 120/240 socket could have connected only ONE hot to both L1 and L2 terminals in the box and have been "legal". That would have had to be an pirate connection, I think you have been told a few "tall tales" from folks who don't understand how the mysteries of electric work.


Actually max power draw on my rig is under 60 amps total both legs combined unless I do some modifications.

But now we are getting to the "I fully agree" part of this discussion

There is NO WAY they can do it and be legal. on this we fully agree.

I was a police dispatcher for over a quarter century if not for Illegal I'd not have had a job.

Side note... My ONAN 5500 has two 30 amp breakers and only one phase the two legs are basically the same, it is a 120 volt only generator.

(That's where I get the 60 amps figure from)


Home is where I park it.
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MEXICOWANDERER

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Posted: 08/02/20 03:56pm Link  |  Quote  |  Print  |  Notify Moderator

Connect an ammeter and see how long the huge draw on hot restart lasts.

BB_TX

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Posted: 08/02/20 04:15pm Link  |  Quote  |  Print  |  Notify Moderator

valhalla360 wrote:

BB_TX wrote:


From the OP:

Our park electrician says that some of the big rigs with 3 ACs and electric everything can sometimes draw more than 50A from a 50A pedestal.

A very simple statement regardless of the intent behind it. And that simple statement is absolutely true, at least until either the park 50 amp breaker trips, or the RV 50 amp breaker trips. And the voltage being used is entirely irrelevant. Doesn't matter whether the RV has any 240 vac appliances or if they are all 120 vac.

Boggles my mind that this has turned into a 9 page (an counting) debate about an "idiot electrician" making a very simple and very true statement and everyone turning that into their own personal interpretation as if they know more about what he was referring to than the electrician himself.

Nothing in your quote states they were referring to 240v operations. Even for big rigs, 240v appliances are very rare.

240 vac has been mentioned multiple times thru the course of this thread. And your own post said the question could not be answered without knowing the voltage. And I still stand on my earlier comments that voltage is irrelevant to the discussion and an RV, whether it has any 240 vac appliances or not, can in fact draw more than 50 amps thru either of the hot legs of the park 50 amp power pedestal until that breaker or the RV 50 amp breaker trips.

MrWizard

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Posted: 08/03/20 12:37am Link  |  Quote  |  Print  |  Notify Moderator

a lot of talk and a lot of opinions along with the facts

the simple truth is : "there is no perfectly 'electrically' balanced RV"
if an RV has (3) A/Cs then one leg has (2) of them

even if it has only (2) A/C's, one on each leg
they will never be pulling exactly the same amount of power on each leg
the converter/charger will be on adding to one leg, other appliances will be used or cycled, so yes its possible to trip the 50amp breaker
IF load management is NOT engaged, manually by human brain or automatically by the RV systems

iirc one member posted here about re-distributing his circuit breaker loads
because it came from the factory with the most used items all on the same leg
somebody at the factory blew it, not properly spreading the load, when they installed the breakers


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valhalla360

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Posted: 08/03/20 01:27pm Link  |  Quote  |  Print  |  Notify Moderator

BB_TX wrote:

valhalla360 wrote:

BB_TX wrote:


From the OP:

Our park electrician says that some of the big rigs with 3 ACs and electric everything can sometimes draw more than 50A from a 50A pedestal.

A very simple statement regardless of the intent behind it. And that simple statement is absolutely true, at least until either the park 50 amp breaker trips, or the RV 50 amp breaker trips. And the voltage being used is entirely irrelevant. Doesn't matter whether the RV has any 240 vac appliances or if they are all 120 vac.

Boggles my mind that this has turned into a 9 page (an counting) debate about an "idiot electrician" making a very simple and very true statement and everyone turning that into their own personal interpretation as if they know more about what he was referring to than the electrician himself.

Nothing in your quote states they were referring to 240v operations. Even for big rigs, 240v appliances are very rare.

240 vac has been mentioned multiple times thru the course of this thread. And your own post said the question could not be answered without knowing the voltage. And I still stand on my earlier comments that voltage is irrelevant to the discussion and an RV, whether it has any 240 vac appliances or not, can in fact draw more than 50 amps thru either of the hot legs of the park 50 amp power pedestal until that breaker or the RV 50 amp breaker trips.


Yes, people are making lots of assumptions about a conversation they were not part of and then calling the guy an idiot without the full story.

There is no evidence the electrician was speaking of 240v draws...so people jumping to the conclusion he was makes no sense. Logically since the vast majority of rigs have NO 240v draws, it would be reasonable to assume he was speaking of 120v draws and in that case, it's very easy for a rig to pull more than 50amps at 120v.

TechWriter

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Posted: 08/03/20 02:41pm Link  |  Quote  |  Print  |  Notify Moderator

valhalla360 wrote:

BB_TX wrote:

valhalla360 wrote:

BB_TX wrote:


From the OP:

Our park electrician says that some of the big rigs with 3 ACs and electric everything can sometimes draw more than 50A from a 50A pedestal.

A very simple statement regardless of the intent behind it. And that simple statement is absolutely true, at least until either the park 50 amp breaker trips, or the RV 50 amp breaker trips. And the voltage being used is entirely irrelevant. Doesn't matter whether the RV has any 240 vac appliances or if they are all 120 vac.

Boggles my mind that this has turned into a 9 page (an counting) debate about an "idiot electrician" making a very simple and very true statement and everyone turning that into their own personal interpretation as if they know more about what he was referring to than the electrician himself.

Nothing in your quote states they were referring to 240v operations. Even for big rigs, 240v appliances are very rare.

240 vac has been mentioned multiple times thru the course of this thread. And your own post said the question could not be answered without knowing the voltage. And I still stand on my earlier comments that voltage is irrelevant to the discussion and an RV, whether it has any 240 vac appliances or not, can in fact draw more than 50 amps thru either of the hot legs of the park 50 amp power pedestal until that breaker or the RV 50 amp breaker trips.


Yes, people are making lots of assumptions about a conversation they were not part of and then calling the guy an idiot without the full story.

There is no evidence the electrician was speaking of 240v draws...so people jumping to the conclusion he was makes no sense. Logically since the vast majority of rigs have NO 240v draws, it would be reasonable to assume he was speaking of 120v draws and in that case, it's very easy for a rig to pull more than 50amps at 120v.


This is the OP & that's what park electrician meant.

Moderators, please close this thread.


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time2roll

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Posted: 08/03/20 02:50pm Link  |  Quote  |  Print  |  Notify Moderator

OK so the pedestal provides 12,000 watts available and the RV draws over 6,000 watts.
What are we even talking about?

Tell the electrician I ran my 700 watt generator to power my 100 watt tv.


2001 F150 SuperCrew
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